Williams fell off the wagon on set of last TV show

Robin Williams fell off the wagon by drinking alcohol on the set of his unsuccessful new TV series, the New York Post has reported.

The comic legend was filming a scene of The Crazy Ones in May last year when he insisted on taping with real alcohol rather than fake booze.

"No one had seen him drinking before this," a source told the newspaper.

"One drink led to another, but it seemed to calm him down."

The newspaper also reported that other cast and crew on the TV comedy were angry at Williams' trademark improvisation instead of sticking to the script.

But co-star Sarah Michelle Gellar wrote a touching tribute to the Oscar winner yesterday, calling him "the father I always dreamed of having".

"There are not enough adjectives to describe the light he was, to anyone that ever had the pleasure to meet him," she said.

"I will miss him everyday, but I know the memory of him will live on."

A longtime friend told the Telegraph Williams was hit hard by the cancellation of The Crazy Ones after just one season.

With a paycheque of more than $150,000 an episode, the show was helping to pay Williams' bills when he was financially struggling.

Despite making four films in his final year of life, Williams was reportedly trying to get out of the movie business and resented having to consider making a sequel to his hit Mrs Doubtfire.